Chapter 21

Heterokontophyta

PHAEOPHYCEAE

The Phaeophyceae, or brown algae, derive their characteristic color from the large amounts of the carotenoid fucoxanthin in their chloroplasts as well as from any phaeophycean tannins that might be present. The chloroplasts also have chlorophylls a, c1, and c2. There are two membranes of chloroplast E.R., which are usually continuous with the

outer membrane of the nuclear envelope. The storage product is laminarin. There are no unicellular or colonial organisms in the order, and the algae are basically filamentous, pseudoparenchymatous, or parenchymatous. They are found almost exclusively in the marine habitat, there being only four genera containing freshwater species, that is,

Heribaudiella, Pleurocladia, Bodanella, and Sphacelaria

(Fig. 21.1) (Schloesser and Blum, 1980). A number of marine forms penetrate into brackish water, where

(a)

(c)

Fig. 21.1 Some freshwater brown algae. (a) Pleurocladia lacustris. (b)

Sphacelaria lacustris. (c) Heribaudiella fluviatilis. (H) Hair; (P) pleurilocular sporangia; (U) unilocular sporangia. ((b) after Schloesser and Blum, 1980.)

(b)